Funds are requested by the Environmental Health Sciences Center (EHS Center) in this application to acquire a High Resolution Mass Spectrometer for shared use and basic research. The instrument would be used to support ongoing EHS Center research in toxicology of environmental chemicals and basic research in chemistry and biochemistry. Specific uses of the instrument would include: (1) linked scan analysis of metastable ions for the identification of positional isomers of polychlorinated phenoxyphenols, polychlorinated hydroxydibenzofurans, and polychlorinated hydroxydioxins in technical pentachlorophenol and isomers of Juvenile hormone photoproducts (2) high resolution mass spectrometry of tropane alkaloids, boromycin, fugal sporulating agents and other natural products, and synthetic intermediates (3) analyses of gluthione conjugates, phospholipids by high resolution mass spectrometry using fast atom bombardment for ionization and (4) analyses of pyrrolizidine alkaloid metabolic conjugates by negative ion fast atom bombardment mass spectrometry.